From 9b3f68b90674419add8be1c0aa740dcdf04f44cc Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Fri, 18 Apr 2008 10:29:51 -0400
Subject: [PATCH] Btrfs: Calculate appropriate chunk sizes for both small and
 large filesystems

Signed-off-by: Chris Mason <chris.mason@oracle.com>
---
 fs/btrfs/volumes.c | 68 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 61 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 93aa36e2436e..e3ddd7fb8edd 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -627,6 +627,27 @@ int btrfs_add_system_chunk(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
+static u64 div_factor(u64 num, int factor)
+{
+	if (factor == 10)
+		return num;
+	num *= factor;
+	do_div(num, 10);
+	return num;
+}
+
+static u64 chunk_bytes_by_type(u64 type, u64 calc_size, int num_stripes,
+			       int sub_stripes)
+{
+	if (type & (BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_DUP))
+		return calc_size;
+	else if (type & BTRFS_BLOCK_GROUP_RAID10)
+		return calc_size * (num_stripes / sub_stripes);
+	else
+		return calc_size * num_stripes;
+}
+
+
 int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *extent_root, u64 *start,
 		      u64 *num_bytes, u64 type)
@@ -643,11 +664,14 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	struct extent_map_tree *em_tree;
 	struct map_lookup *map;
 	struct extent_map *em;
+	int min_chunk_size = 8 * 1024 * 1024;
 	u64 physical;
 	u64 calc_size = 1024 * 1024 * 1024;
-	u64 min_free = calc_size;
+	u64 max_chunk_size = calc_size;
+	u64 min_free;
 	u64 avail;
 	u64 max_avail = 0;
+	u64 percent_max;
 	int num_stripes = 1;
 	int sub_stripes = 0;
 	int looped = 0;
@@ -666,6 +690,8 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	if (type & (BTRFS_BLOCK_GROUP_RAID1)) {
 		num_stripes = min_t(u64, 2,
 				  btrfs_super_num_devices(&info->super_copy));
+		if (num_stripes < 2)
+			return -ENOSPC;
 	}
 	if (type & (BTRFS_BLOCK_GROUP_RAID10)) {
 		num_stripes = btrfs_super_num_devices(&info->super_copy);
@@ -674,13 +700,45 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		num_stripes &= ~(u32)1;
 		sub_stripes = 2;
 	}
+
+	if (type & BTRFS_BLOCK_GROUP_DATA) {
+		max_chunk_size = 10 * calc_size;
+		min_chunk_size = 256 * 1024 * 1024;
+	} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
+		max_chunk_size = 4 * calc_size;
+		min_chunk_size = 64 * 1024 * 1024;
+	} else {
+		min_chunk_size = 32 * 1024 * 1024;
+	}
+
+	/* we don't want a chunk larger than 10% of the FS */
+	percent_max = div_factor(btrfs_super_total_bytes(&info->super_copy), 1);
+	max_chunk_size = min(percent_max, max_chunk_size);
+
+	if (calc_size * num_stripes > max_chunk_size) {
+		calc_size = max_chunk_size;
+		do_div(calc_size, num_stripes);
+		do_div(calc_size, stripe_len);
+		calc_size *= stripe_len;
+	}
+	/* we don't want tiny stripes */
+	*num_bytes = chunk_bytes_by_type(type, calc_size,
+					 num_stripes, sub_stripes);
+	calc_size = max_t(u64, chunk_bytes_by_type(type, min_chunk_size,
+		          num_stripes, sub_stripes), calc_size);
+
 again:
+	do_div(calc_size, stripe_len);
+	calc_size *= stripe_len;
+
 	INIT_LIST_HEAD(&private_devs);
 	cur = dev_list->next;
 	index = 0;
 
 	if (type & BTRFS_BLOCK_GROUP_DUP)
 		min_free = calc_size * 2;
+	else
+		min_free = calc_size;
 
 	/* build a private list of devices we will allocate from */
 	while(index < num_stripes) {
@@ -727,13 +785,9 @@ again:
 	}
 
 	stripes = &chunk->stripe;
+	*num_bytes = chunk_bytes_by_type(type, calc_size,
+					 num_stripes, sub_stripes);
 
-	if (type & (BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_DUP))
-		*num_bytes = calc_size;
-	else if (type & BTRFS_BLOCK_GROUP_RAID10)
-		*num_bytes = calc_size * (num_stripes / sub_stripes);
-	else
-		*num_bytes = calc_size * num_stripes;
 
 	index = 0;
 printk("new chunk type %Lu start %Lu size %Lu\n", type, key.offset, *num_bytes);